1942 were linked by re-encipherments, but the only
Heer
cipher to produce cillies consistently in 1942 was Osprey which, although classified as a
Heer
cipher by Hut 6, was really the cipher of the Todt construction organization, which may explain its poor operating practices.
No repeats of key-lists were discovered in
Heer
traffic in 1941 or 1942. The success rate (decrypts as a percentage of the signals intercepted) against
Luftwaffe
traffic fell from 92 per cent in November 1941 to 50 per cent in November 1942, largely because Light Blue went out of service in January 1942, and the main
Luftwaffe
traffic started to use eight or more ciphers. During 1942, the success rate against
Heer
traffic was only 0.6 per cent (a mere thirty decrypts) in January but rose to 27 per cent in May. Intercepts of all Hut 6 traffic increased from 32,000 per month in September 1941 to 82,000 in November 1942. The overall percentage of the traffic (
Luftwaffe
,
Heer
and Railway) broken by Hut 6 remained around 50 per cent of the total intercepts in 1942. Unidentified traffic, where Hut 6 did notknow which cipher was being used, was reduced from 17 per cent of the total traffic in September 1941 to only 2.4 per cent in November 1942, illustrating Hut 6’s and the Y service’s increasing mastery of the
Luftwaffe
and
Heer
radio nets, and their skill in reconstructing the extensive lists of cipher discriminants used by them.
SS decrypts increased considerably in 1942 following the discovery in April that daily reports (codenamed HOR-HUG by Bletchley Park) of concentration camp numbers provided half the Orange
Stecker
. The HOR-HUG reports gave the numbers of people in certain concentration camps, which were encoded by a letter for digit substitution (so providing ten letters – the first five
Stecker
pairs), but ceased in early 1943, after which the reports were sent by land line. Orange keys could often be broken with an unused part of a bombe, while the other parts were being used for a different cipher.
Hut 6 also solved the Railway traffic in eastern Europe (later codenamed Rocket) in 1941 and 1942. The traffic used a rewired version of commercial Enigma, without
Stecker
, and was therefore relatively easy to solve using hand methods. Lt. Col. John Tiltman first broke the traffic around the end of July 1940, after which the wiring of the machine was solved by Hut 8, which became responsible for reading the traffic until the work was later transferred to Hut 6. All 2,300 messages received in July and August 1940 were solved. The traffic ceased at the end of August, but began to be intercepted again in February 1941. The 90 per cent success rate against it in 1942 was the highest for all Hut 6 Enigma.
Hut 6 largely consolidated its position during 1943. However, it faced a significant challenge when the
Heer
stopped using discriminants in Enigma traffic on 1 September, and the
Luftwaffe
followed suit on 1 November. The small change represented a major improvement in security, since Hut 6 was now faced with 3,000 or so signals daily, all of which apparently used the same cipher but which in fact employed up to ninety different ciphers. The new procedure slowed Hut 6 quite considerably, and required it to increase its registration and decoding room staff substantially, from about 220 to 300. Hut 6 and the Y service were able to meet the challenge only because they had become highly experienced and very flexible organizations, capable of responding to any change quickly and efficiently.
In addition, Hut 6 had to prepare for the second front in late 1943 and early 1944. It identified many of the
Heer
’
s
Enigma ciphers andtheir related frequencies and call signs with the help of the Y service, although it had little success in solving them before the Normandy landings in June, and thought that most of its intelligence on the
Heer
might have to be derived from Red and Flivo
(Heer-Luftwaffe
liaison) ciphers. Fortunately, some of the
Heer
ciphers
Heer
cipher to produce cillies consistently in 1942 was Osprey which, although classified as a
Heer
cipher by Hut 6, was really the cipher of the Todt construction organization, which may explain its poor operating practices.
No repeats of key-lists were discovered in
Heer
traffic in 1941 or 1942. The success rate (decrypts as a percentage of the signals intercepted) against
Luftwaffe
traffic fell from 92 per cent in November 1941 to 50 per cent in November 1942, largely because Light Blue went out of service in January 1942, and the main
Luftwaffe
traffic started to use eight or more ciphers. During 1942, the success rate against
Heer
traffic was only 0.6 per cent (a mere thirty decrypts) in January but rose to 27 per cent in May. Intercepts of all Hut 6 traffic increased from 32,000 per month in September 1941 to 82,000 in November 1942. The overall percentage of the traffic (
Luftwaffe
,
Heer
and Railway) broken by Hut 6 remained around 50 per cent of the total intercepts in 1942. Unidentified traffic, where Hut 6 did notknow which cipher was being used, was reduced from 17 per cent of the total traffic in September 1941 to only 2.4 per cent in November 1942, illustrating Hut 6’s and the Y service’s increasing mastery of the
Luftwaffe
and
Heer
radio nets, and their skill in reconstructing the extensive lists of cipher discriminants used by them.
SS decrypts increased considerably in 1942 following the discovery in April that daily reports (codenamed HOR-HUG by Bletchley Park) of concentration camp numbers provided half the Orange
Stecker
. The HOR-HUG reports gave the numbers of people in certain concentration camps, which were encoded by a letter for digit substitution (so providing ten letters – the first five
Stecker
pairs), but ceased in early 1943, after which the reports were sent by land line. Orange keys could often be broken with an unused part of a bombe, while the other parts were being used for a different cipher.
Hut 6 also solved the Railway traffic in eastern Europe (later codenamed Rocket) in 1941 and 1942. The traffic used a rewired version of commercial Enigma, without
Stecker
, and was therefore relatively easy to solve using hand methods. Lt. Col. John Tiltman first broke the traffic around the end of July 1940, after which the wiring of the machine was solved by Hut 8, which became responsible for reading the traffic until the work was later transferred to Hut 6. All 2,300 messages received in July and August 1940 were solved. The traffic ceased at the end of August, but began to be intercepted again in February 1941. The 90 per cent success rate against it in 1942 was the highest for all Hut 6 Enigma.
Hut 6 largely consolidated its position during 1943. However, it faced a significant challenge when the
Heer
stopped using discriminants in Enigma traffic on 1 September, and the
Luftwaffe
followed suit on 1 November. The small change represented a major improvement in security, since Hut 6 was now faced with 3,000 or so signals daily, all of which apparently used the same cipher but which in fact employed up to ninety different ciphers. The new procedure slowed Hut 6 quite considerably, and required it to increase its registration and decoding room staff substantially, from about 220 to 300. Hut 6 and the Y service were able to meet the challenge only because they had become highly experienced and very flexible organizations, capable of responding to any change quickly and efficiently.
In addition, Hut 6 had to prepare for the second front in late 1943 and early 1944. It identified many of the
Heer
’
s
Enigma ciphers andtheir related frequencies and call signs with the help of the Y service, although it had little success in solving them before the Normandy landings in June, and thought that most of its intelligence on the
Heer
might have to be derived from Red and Flivo
(Heer-Luftwaffe
liaison) ciphers. Fortunately, some of the
Heer
ciphers
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